Processing methods including forming dielectric layers for electrical isolation in integrated circuits have been described. One example is thermal oxidation of silicon in a wet or dry oxidation process at a temperature between 800° C. and 1200° C. to form silicon dioxide, in which water vapor (steam) or molecular oxygen, respectively, is used as the oxidant or catalyst. Wet or dry thermal oxidation of silicon can yield a pure, high-quality, amorphous oxide, with a density of 2.2 g/cm3. However, the high temperatures used in thermal oxidation can make this process unsuitable for certain applications. In addition, costs associated with high-temperature processes can be prohibitive.
Processes to form silicon dioxide layers at lower temperatures have been described. For example, U.S. Pat. No. 3,850,687 to Wern, which is incorporated by reference herein, describes densification of a silicate glass that has been deposited on a substrate as a layer from the vapor phase. Densification of the silicate glass includes heating the glass layer at a temperature on the order of about 400° C. to 450° C. in an atmosphere of water vapor. In “Silicon Nitride and Silicon Dioxide Thin Insulating Films: Proceedings of the Symposium on Silicon Nitride and Silicon Dioxide Thin Insulating Films” by M. J. Deen, which is incorporated by reference herein, annealing chemical vapor deposited silicon dioxide films in the range of 250° C. to 400° C. in a steam ambient was shown to improve stress stability of the silicon dioxide films. U.S. Pat. No. 7,521,378 to Fucsko et al., which is incorporated by reference herein, describes a low temperature process for polysilazane oxidation/densification. The process includes depositing a polysilazane solution on a substrate and processing with ozone in a wet oxidation at a temperature less than about 100° C. to chemically modify the polysilazane material to a silicon oxide layer. These silicon oxide layers, however, lack some of the desirable physical properties of more dense silicon oxide layers formed by thermal oxidation.
Nanofabrication includes the fabrication of very small structures that have features on the order of 100 nanometers or smaller. One application in which nanofabrication has had a sizeable impact is in the processing of integrated circuits. The semiconductor processing industry continues to strive for larger production yields while increasing the circuits per unit area formed on a substrate, therefore nanofabrication becomes increasingly important. Nanofabrication provides greater process control while allowing continued reduction of the minimum feature dimensions of the structures formed. Other areas of development in which nanofabrication has been employed include biotechnology, optical technology, mechanical systems, and the like.